locations.putAll(sourceDominant ? sourceLocations : targetLocations);
        }

        return new InputLocation(-1, -1, InputSource.merge(source.getSource(), target.getSource()), locations);
    } // -- InputLocation merge( InputLocation, InputLocation, boolean )

    /**
     * Merges the {@code source} location into the {@code target} location.

     *
     * @return The hint about the source of the problem or an empty string if unknown, never {@code null}.
     */
    String getSource();

    /**
     * Gets the one-based index of the line containing the problem. The line number should refer to some text file that
     * is given by {@link #getSource()}.
     *
     * @return The one-based index of the line containing the problem or a non-positive value if unknown.
     */

     *
     * @return The hint about the source of the problem or an empty string if unknown, never {@code null}.
     */
    String getSource();

    /**
     * Gets the one-based index of the line containing the problem. The line number should refer to some text file that
     * is given by {@link #getSource()}.
     *
     * @return The one-based index of the line containing the problem or a non-positive value if unknown.
     */

        collector.add(null, "PROBLEM3", -1, -1, null);

        assertEquals("", collector.getProblems().get(0).getSource());
        assertEquals("SOURCE_PROBLEM2", collector.getProblems().get(1).getSource());
        assertEquals("SOURCE_PROBLEM3", collector.getProblems().get(2).getSource());
    }

        this.exception = exception;
    }

    public String getSource() {
        return source;
    }

    public int getLineNumber() {
        return lineNumber;
    }

    public int getColumnNumber() {
        return columnNumber;
    }

    public String getLocation() {
        StringBuilder buffer = new StringBuilder(256);

        if (!getSource().isEmpty()) {
            if (buffer.length() > 0) {

            if (request.getPath().isPresent()) {
                Path path = request.getPath().get();
                res = builder.build(path.toFile(), req);
            } else if (request.getSource().isPresent()) {
                Source source = request.getSource().get();
                ModelSource2 modelSource = new SourceWrapper(source);
                res = builder.build(modelSource, req);
            } else {

            if (req.getLocation().getSource() != null) {
                modelId = req.getLocation().getSource().getModelId();
                source = req.getLocation().getSource().getLocation();
            }
        }

        if (modelId == null) {
            modelId = getModelId();
            source = getSource();
        }

    @Override
    public String getLocation() {
        StringBuilder buffer = new StringBuilder(256);

        if (!getSource().isEmpty()) {
            if (buffer.length() > 0) {
                buffer.append(", ");
            }
            buffer.append(getSource());
        }

        if (getLineNumber() > 0) {
            if (buffer.length() > 0) {
                buffer.append(", ");
            }

     * @return the hint about the source of the problem or an empty string if unknown, never {@code null}
     */
    @Nonnull
    String getSource();

    /**
     * Gets the one-based index of the line containing the problem. The line number should refer to some text file that
     * is given by {@link #getSource()}.
     *
     * @return the one-based index of the line containing the problem or a non-positive value if unknown
     */

                FileModelSource source = getSource(groupId, artifactId);
                if (source == null) {
                    // we need to check the whole reactor in case it's a dependency
                    loadFullReactor();
                    source = getSource(groupId, artifactId);
                }
                if (source != null) {